IMAP source improvements

- Support multiple STORE commands. Defaults to +FLAGS (\Deleted)
  to conserve current behavior.
- Support custom search criteria. Defaults to NOT DELETED
  to converse current behavior.
- Support enabling/disabling IMAP expunge command
  after each message. Defaults to True to conserve
  current behavior.
- Increase functionality of the MockIMAPServer

Signed-off-by: Roberto Rosario <roberto.rosario@mayan-edms.com>

docs/releases/3.3.rst

@@ -89,6 +89,14 @@ Changes
 - Unify all line endings to be Linux style.
 - Add support for changing the system messages position.
   GitLab issue #640. Thanks to Matthias Urhahn (@d4rken).
+- Add support for custom IMAP search criteria.
+- Add support for executing custom IMAP STORE commands
+  on processed messages.
+- Add support for specifing a destination IMAP mailbox for
+  processed messages. GitLab issue #399. Thanks to
+  Robert Schöftner (@robert.schoeftner).
+- Add support to execute the IMAP expunge command after each
+  processed message.
 
 Removals
 --------
@@ -200,6 +208,7 @@ Backward incompatible changes
 Bugs fixed or issues closed
 ---------------------------
 
+- :gitlab-issue:`399` Archive of processed e-mails
 - :gitlab-issue:`526` RuntimeWarning: Never call result.get() within a task!
 - :gitlab-issue:`532` Workflow preview isn't updated right after transitions are modified
 - :gitlab-issue:`540` hint-outdated/update documentation